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A friend suggested that one of the reasons we love dogs so much is that they can’t talk back. But I wonder whether that’s true. Sure, a dog won’t tell you, “You really shouldn’t have that second cookie,” but does that mean dogs are not talking back?

Dogs are anything but mute, and while we usually focus on wagging tails and beguiling eyes, vocalizations—among them, barks and growls—provide us with another window into dogs’ everyday experiences.

Social species are known to be much noisier than animals who lead solitary lives. Snow leopards roam the mountains of central Asia in near silence, but groups of monkeys do a lot of highvolume chattering. So, given that dogs and their wild progenitor, the wolf, are über-social, it’s no surprise that both produce a wide range of vocalizations: they bark, whine, whimper, howl, huff, growl, yelp and yip (among other nuanced sounds). From the earliest moments of their lives, dogs and their canid relatives produce tonal yelps and whines, and atonal barks and grunts appear in the fi rst few weeks of life in conjunction with the onset of social behavior.

There’s a big difference between the bark of an adult dog and that of an adult wolf, however. Dogs seem to play every instrument in the orchestra, hitting the highs of the flute and the lows of the tuba, sometimes with the duration of a Wagnerian opera. Plus, there seems to be no context in which a dog won’t bark: They bark when alone and with other dogs. Some bark before, during and even after a ball is thrown. A car goes by or the doorbell rings and barking ensues. In contrast, wolves bark less frequently and in fewer contexts, primarily for warning or defense.

Meanings Behind the Message
What do canine vocalizations mean? Animal behavior researchers have only recently begun to chip away at this question. As Monique Udell, PhD, who is currently a faculty fellow at the University of Oregon, refl ects, “Vocal behavior in other species has received a lot of detailed attention. In birds, we’ve looked down to the note sequence and explored tiny variations. Vocalizations are such a prominent feature of dogs, and there is a lot to learn.” To date, dog vocalizations have not received comparable scrutiny.

That being said, research that has been conducted on the subject is incredibly insightful. Take growls, which, it has been shown, dogs use to accurately judge another dog’s size. How in the world do we know that? Tamás Faragó, PhD, and his colleagues at the Family Dog Project at Eötvös Loránd University in Budapest (familydogproject.elte.hu) presented dogs with two images of the same dog: one was true to size and another was 30 percent larger or smaller. Dogs then listened to a pre-recorded growl, and most dogs looked at the image of the full-size dog rather than the altered image.

Growls appear to be meaningful in other ways as well. In another study, Faragó and his colleagues used some clever trickery to explore how dogs respond to growls recorded in different situations. In an apparently empty room, a dog was allowed to approach a bone. Unbeknownst to the dog, there was a speaker hidden behind the bone, and as the dog approached, the sound of a “play growl,” a “stranger-approaching” growl or a “food-guarding” growl was transmitted through it. Dogs were likely to take the bone when hearing the “stranger-approaching” or “play” growl, but the food-guarding “my bone” growl deterred them. Even though the foodguarding and stranger-approaching growls sound quite similar (at least, to our ears), they prompted different behavior.

Many studies investigating vocalizations are based on prerecorded samples, but it is important to remember that vocalizations and visual signals usually go hand-in-hand. In the strangerapproaching context, dogs growled with closed mouths, whereas in fooddefense situations, they showed their teeth and pulled back their lips.

While we tend to take notice when we hear a growl, we often dismiss barking as meaningless noise, as though it is simply an item on a dog’s daily checklist: “Take a walk, have breakfast, bark.” Before the turn of the century, that was the prevailing view among researchers and theorists. At most, barking was thought to result from social facilitation— one dog barking prompts other dogs to bark—or maybe attentionseeking, or even rivalry or defense.